What should the resistance of the HT coil wire be?

[mintscorpion]

I am trying to diagnose a no start condition on my 1986 325e. I have tested several things including the coil which I believe is in spec. I also tested the high-tension coil lead that goes from the coil to the distributor. The reading was around 1.9k ohms. I know on spark plug wires the resistance should be about 1k ohms per foot. Is this the same for the HT coil lead?

My other question is, if the coil is good and the HT coil lead is good and there is a steady flow of fuel, what else is left to be bad. I'm thinking the DME could be shot but I am not sure.

Thank you in advance.

[PeaveyBassist]

Make sure you have spark to begin with. Just because fuel gets to the fuel rail doesn't mean the injectors are opening.

[10yre30r]

Well, if there is spark and fuel . It could be a multitude of things. Is your engine turning over when you try to start it ? Take off the oil cap and have some one start the engine make sure when they do that the lifters and springs move when they do. That way you know that your timing belt is not broke. I think it could be a sensor like MAF or Crank sensor or Dme ......Im sure a few of the pro's on this forum will weigh in...

[ZombiE30]

Make sure you have spark to begin with. Just because fuel gets to the fuel rail doesn't mean the injectors are opening.

+1

according to bentley, the coil wire should be about 1000 ohms +/- 200. So, you're close. You may want to consider replacing them, but as long as there's no corrosion on the connectors, I don't think this would automatically cause a no-start condition.

Get a mechanic's stethoscope or some other means to listen to the injectors when cranking. If they make a rapid clicking then you know they are opening and closing.

Since this is an eta, also check the two reference sensors that go into the transmission bellhousing. Their connections are those two things bolted to the rear of the valve cover. I'm pretty sure they're supposed to be around 960 ohms each.

Pull a spark plug and ground it to the intake manifold when trying to start it. Can you see/hear spark? If not, then you may want to pull the DME connector and check all of it's circuits with an ohmmeter. Bentley is useful here.
If those check out too, then it's the DME at fault.

ps-My '85 eta has a no-start condition when it's under 35 degrees out caused by old cranky transistors in the DME. As long as I can warm up the DME, my car starts fine.

Ask me how I do it.....

(to be continued)

[mintscorpion]

First of all thanks to everyone for your help especially zombiE30.
I used a stethoscope on the injectors and nothing. So this means there is no spark and no fuel. So I am assuming this must indicate either a bad DME or DME relay. I think I will try to replace the relays first. Out of the three in the smaller relay box, which one is the DME relay? And can i use on of the relays from the fuse box to test this?

Tnank you again.

[ZombiE30]

Actually, no spark AND no fuel could mean those sensors I mentioned above as well.....

Did you check those two connectors on the valve cover, that lead to the sensors in the bellhousing of the transmission? One of those being out would cause this.

The Bentley is not entirely clear on relay location either. It lists Fuel Pump, Main Relay, O2 Sensor Heater Relay in that order, which I'm assuming is L to R. However, Jlevie answered differently in your other post, so I'd go with that.

to test the relay, just connect battery positive to terminal 85 and ground to termnal 86. You should hear a click. If there is no click, the relay is bad.
After the click, put an ohmmeter across terminal 30 and 87. The resistance should be almost 0 (indicating a good circuit path).

[mintscorpion]

Ok, so i tested the relay and it clicked twice and then no more. I'm not sure why.

As for those two connectors, I am not seeing them on the valve cover. I do see two connectors on the engine block, in front of the starter that have wires that lead to the transmission, is it possible that on my year they were mounted in this location. If not, what do they look like?

I feel like an idiot for not being able to figure this out. Thank you again for your help ZombiE30!

[ZombiE30]

The relay: It should only click once each time you energize it. Did it do the same thing during repeated tests? I'd replace that just to be safe, because that sounds a little fishy.

Weird. Maybe it's just '85 and earlier that have the connectors mounted on the valve cover.
In any case, find the two sensors in the bell housing, and find wherever they have a connection. Pull that apart and check the resistance of both sensors. As mentioned above, they should be 960 ohms +/- 96. Anything outside of that, and they need to be replaced.

If all of that checks out, then you need to start looking at your DME or considering the possibility that the reference pin on your flywheel came out. I'm not sure how to check that, so let's just hope it's a sensor for now. =)

[mintscorpion]

Well, it runs again. I went to the local pick a part this morning and they happened to have an '86 325e so I pulled the DME. I put it in and my e30 fired right up. I think I got lucky because I only paid $35 for the DME.

Thanks for all the help ZombiE30!

[ZombiE30]

Nice find, dude!
I tried that once and I pulled one that worked worse than my current one. :(

Just keep an eye on it when it gets really cold. These DMEs are starting to wear out a little bit, and mine won't start if it's below 35 degrees.

At least now you know all your other stuff is good!

You're welcome and happy riding!